Breaker, safety circuit and secondary battery pack

1 . A breaker comprising:

a fixed piece which has a fixed contact;

a movable piece which has an elastic portion being elastically deformable, and a movable contact in one end portion of the elastic portion, and which presses the movable contact so as to contact with the fixed contact;

a thermally-actuated element which is deformed in response to temperature changes so as to shift the movable piece from a conductive state in which the movable contact contacts with the fixed contact to a cut-off state in which the movable contact is separated from the fixed contact; and

a resin case which has a recessed portion for accommodating the thermally-actuated element,

wherein

the fixed piece has an embedded portion which is embedded in the resin case in a region which, in a plan view viewed in a thickness direction of the fixed piece, overlaps with the thermally-actuated element, and

the resin case has

an outer peripheral portion which is formed on the outer perimeter of the recessed portion,

a first penetrating portion which penetrates the recessed portion so as to expose the embedded portion to a thermally-actuated element side, and

an island portion which is, in an inside of the first penetrating portion, interposed between the fixed piece and the thermally-actuated element, and

a connecting portion which connects between the outer peripheral portion and the island portion.

2 . The breaker as set forth in claim 1 , wherein

the connecting portion comprises a rib protruding toward the thermally-actuated element.

3 . The breaker as set forth in claim 1 , wherein

the fixed piece has a through-hole, and

the outer peripheral portion and the connecting portion are connected by resin filled in the through-hole.

4 . The breaker as set forth in claim 1 , wherein

the resin case has a bottom portion covering the bottom a bottom surface of the fixed piece, and a window portion penetrating the bottom portion to expose the bottom surface.

5 . The breaker as set forth in claim 1 , which further comprises

a positive characteristic thermistor, and

the island portion is provided with a second penetrating portion for mounting the positive characteristic thermistor so that the fixed piece and the thermally-actuated element are electrically connected through the positive characteristic thermistor.

6 . The breaker as set forth in claim 5 , wherein

the connecting portion includes

first connecting portions extending from the island portion to opposite sides in a longer direction of the movable piece, and

second connecting portions extending from the island portion to opposite sides in a shorter direction of the movable piece.

7 . The breaker as set forth in claim 1 , wherein

the connecting portion includes a third connecting portion extending in a longer direction of the movable piece from the island portion toward a side opposite to the fixed contact.

8 . The breaker as set forth in claim 7 , wherein

the resin case comprises protruding portions protruding from the island portion to opposite sides in the shorter direction of the movable piece.

9 . The breaker as set forth in claim 8 , wherein

the protruding portions terminate before the outer peripheral portion.

10 . A breaker comprising:

a fixed piece which has a fixed contact;

a movable piece which has an elastic portion being elastically deformable, and a movable contact in one end portion of the elastic portion, and which presses the movable contact so as to contact with the fixed contact;

a thermally-actuated element which is deformed in response to temperature changes so as to shift the movable piece from a conductive state in which the movable contact contacts with the fixed contact to a cut-off state in which the movable contact is separated from the fixed contact; and

a resin case which has a recessed portion for accommodating the thermally-actuated element,

wherein

the fixed piece has an embedded portion which is embedded in the resin case in a region which, in a plan view viewed in a thickness direction of the fixed piece, overlaps with the thermally-actuated element, and

the resin case has

an outer peripheral portion which is formed on the outer perimeter of the recessed portion,

a first penetrating portion which penetrates the recessed portion so as to expose the embedded portion to a thermally-actuated element side, and

an island portion which is, in an inside of the first penetrating portion, interposed between the fixed piece and the thermally-actuated element,

a bottom portion which covers a bottom surface of the fixed piece, and

a window portion which penetrates the bottom portion and exposes the bottom surface.

11 . The breaker as set forth in claim 10 , wherein

the first penetrating portion and the window portion partially overlap in the plan view.

12 . The breaker as set forth in claim 1 , wherein

the thermally-actuated element is formed in a rectangular shape in the plan view, and

the first penetrating portion is provided at positions opposed to the to four corners of the thermally-actuated element.

13 . A safety circuit for an electrical device, comprising the breaker as set forth in claim 1 .

14 . A secondary battery pack comprising the breaker as set forth in claim 1 .

15 . A safety circuit for an electrical device, comprising the breaker as set forth in claim 10 .

16 . A secondary battery pack comprising the breaker as set forth in claim 10 .